This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Understanding assembly of virus capsids has applications for understanding virus biology, development of assembly-directed antiviral therapeutics, and development of nanotechnology. In this proposal we request time to collect data on hepatitis B virus (HBV) capsids complexed with small molecules that affect assembly. This will define the respective binding sites of these assembly effectors and will allow us to deduce a mechanism of action. We will also acquire data for the structure of a plant virus capsid that was assembled on a nanoparticle core. This structure will provide insight into the virus-core interaction and as importantly provide a testbed for defining the experimental peculiarities of determining the structure of such hybrid particles. More than 350 million individuals suffer from chronic HBV, 1 million in the United States. HBV contributes 600,000 deaths each year. We have identified assembly of the HBV capsid as an antiviral target. In vivo, correct assembly is critical to viral replication. Recently we determined the structure of HBV capsids with a small molecule assembly effector and were able to determine the binding site and elucidate the thermodynamic basis of activity. We have identified a new family of effectors that induce assembly of smaller than normal capsids. Crystals of these complexes have diffracted up to 5.5[unreadable] resolution on a home source;typically we have improved resolution of virus crystals by 1.5 to 2.5[unreadable] using synchrotron radiation. We have also investigated assembly of virus-based nanostructures. In collaboration with Bogdan Dragnea (also at Indiana University), we have obtained crystals of Brome Mosaic Virus capsid protein that were assembled in vitro on a PEGylated gold nanoparticle. Here we can ask how intimately the protein and substrate interact. All samples used in these experiments are virus-like particles, not infectious virions.